Rel storm III or Stadium III.

I have a Storm III and it is nice... I always long for more definition with sub base - I made the mistake of listening to the Studio III - kind of upset my "apple cart" :). I would just wait and get the Stadium III (used for less $$) when you have a chance... I am not familiar with the M&K so I cannot comment on the differences vs. the REL ST line...

May want to consider 2 subs if your main focus is music...

A friend tells me that 2 properly configured Vandersteen 2Wq subs work GREAT for music and the jury for Home Theater... as there are possible HT processor issues in his system... Since it sounds like you may be in the middle of a wait - send me an E-MAIL and I will let you know when my friend has his HT figured out...

It this a home theater question? If you don't do much 2 channel listening, maybe you should take a look at the REL Q400E or Q401E.

The Stadium III is a decent step up from the Storm III. You get what you pay for..

I had an M&K MX-150 with VA Bach's and I too wanted a better sub for music. I just didn't have the crossover flexibility with the M&K. I picked up a Storm III and cannot say enough about how much of a difference it made. I always heard bass is supposed to be non-directional, or is it omni-directional, but with the M&K's high xover I could sense where it was coming from, not with the REL, I feel the kick and the bass sounds like it's coming from right in front of me, which it isn't it's in the same corner where the M&K was.
Can't comment on the differences between the two subs. I'm more than happy with the Storm. I guess it would depend on how much power you really need to match your room and main amp/speakers.
Call Sumiko since they import both brands. That is the same advice someone gave me a few months back. I took it and they answered all my questions even knowing I bought the sub second hand.
Since this is an HT forum, it rocks for movies too!